1. Field of the Invention
This invention relates to custom designed hearing instruments and other ear devices and methods for making them. Such hearing instruments include devices commonly called hearing aids. Other ear devices include, for example, musician's custom ear monitors and custom fit ear pieces for personal communication devices such as cell phones, PDAs, digital audio playback devices for music or portable audio/video equipment and custom fit language translators. More specifically, this invention relates to tailoring the physical characteristics of a hearing instrument to produce desired sound frequency responses.
2. Background Art
Current hearing instrument technology is based upon the analog or digital amplification of sound. Hearing instruments simply incorporate various mechanical and/or electrical technologies to assist the hearing impaired to hear amplified sound. As both the electronic and manufacturing technologies have advanced, however, these hearing instrument devices have become increasingly smaller and less onerous for the hearing impaired. Several types of hearing aid instruments are in use today, including, but not limited to, the “behind-the-ear” (BTE) and “in-the-ear” (ITE) hearing aids. The BTE hearing aid, for example, consists of an “ear hook” having an electronics module (i.e. a microphone, amplifier, receiver, etc.) worn primarily behind the ear while an ear canal tube carrying the amplified sound is directed into the wear's ear canal. Original BTE designs used an ear mold to hold the ear canal tube in the proper position within the wearer's ear canal. More recent BTE designs use a barb or other rigid attachment that extends outward from the ear canal tube and lodges behind the tragus to maintain the proper positioning of the ear canal tube within the wearer's ear canal. An advantage of the more recent BTE designs is that the wearer's ear canal is not occluded by an ear canal mold, which may block the passage of nearly all unamplified outside sounds.
Advances in hearing aid design have led to the development of miniature hearing aid housings which can be worn inside the ear rather than on the outside of the ear. These miniature housings fit within the canal portion of the wearer's ear and take the place of the BTE-type ear hook housing and tubing-connected ear mold. Because the entire hearing aid device is inserted within the wearer's ear, the wearer has the benefits of a functional hearing aid instrument which is less outwardly noticeable than traditional BTE designs. “In the ear” (ITE)-type hearing devices have grown in popularity in recent years, mainly because the wearer feels less stigmatized when the hearing instrument is more or less inconspicuous. However, ear canal occlusion can also be a problem with these more recent ITE-type hearing aid devices in which the entire electronics module (i.e. a microphone, amplifier, receiver, etc.) is located within the ear mold.
Many of the advances in hearing instrument technology continue to be spurred by the comfort needs of the wearer. For example, vent channels have been designed into many ear molds to mitigate the problem of ear canal occlusion. These vent channels extend through the ear piece and are intended to promote wearer comfort. The smallest vent, called a pressure vent, promotes wearer comfort by allowing air to enter the ear canal thereby maintaining atmospheric pressure in the ear canal while the ear piece is in place. Large vents, however, have an effect on the acoustic response of the device. A pressure vent has little effect on acoustic response. But vents with larger diameters reduce some of the low frequency sounds amplified by the hearing aid by providing an alternative path of lesser acoustic resistance. Larger vents also mitigate the occlusion effect caused by an ear piece that completely fills the outer portion of the ear canal. The occlusion effect occurs when bone-conducted sound vibrations from a speaker's own voice become trapped between the ear piece and the ear drum thus producing what is perceived by the speaker to be a “hollow” or “booming” sounding voice. Partial ear occlusion can be somewhat beneficial, however, in that feedback is reduced. Some hearing instrument manufacturers provide for venting of the ear mold shell, but the venting is generally limited to a few standard sizes because of geometric challenges and manufacturing inefficiencies. When custom hearing instruments or ear molds are produced, certain features of the instruments are standardized to better accommodate the capabilities of the assembly line process in the hearing instrument or ear mold production facility.
Rather than tailoring the physical characteristics of the hearing device to emphasize desired frequencies, the prior art has generally been concerned with electronically “tuning” the hearing device using the then available amplification circuitry. An audiometric evaluation is usually conducted to determine the user's frequency response function, usually a graph of amplitude versus frequency. This information is used to select an amplification circuit from a number of standardized circuits and/or to adjust the frequency response of the chosen electronic amplification circuit in order to boost the amplification at those frequencies where the user is the most hearing impaired.
As previously mentioned, the prior art BTE hearing aid instruments comprise an ear hook which houses an electronics module (i.e. a microphone, amplifier, receiver, etc.). The ear hook is worn on the outside of a user's ear and an ear mold, attached to the ear hook by tubing, is worn in the user's ear canal. The tubing conducts sound from the receiver of the ear hook to a bore in the ear mold for transmission to the user's eardrum. The ear hook amplifier typically includes a wideband frequency response. A 1981 paper published in the Journal of Speech and Hearing Disorder titled, “Earmold Options for Wideband Hearing Aides” by Mead C. Killian describes how this tubing of various sizes and geometries within the bore or sound channel of the ear mold can be selected to affect the high frequency response of the hearing aid.
U.S. patent publication US-2006-0115105-A1 to Brumback et al. discloses a method and apparatus for tailoring the audio frequency response of an ITE hearing instrument by altering the physical characteristics of the device to more accurately compensate for a user's specific hearing loss. More specifically, the bore of ITE hearing instrument, providing a passageway for the transmission of sound from the internal receiver to the user's eardrum, is custom-designed in various shapes, for example, a cone, to emphasize desired sound frequencies. This U.S. Patent Publication US-2006-0115105-A1 is hereby incorporated by reference.
U.S. Pat. No. 6,275,596 to Fretz et al. discloses an apparatus for varying the frequency response in a BTE hearing instrument. The disclosed apparatus is a variably-shaped “tip” disposed at the end of the ear canal tubing placed within the user's ear canal. The tip, which can be a separate component which fits over the end of the ear canal tube or is formed therein, may be flared or have an acoustic damper to smooth and reduce peaks in the frequency response of the hearing instrument device. Fretz et al. provide several examples of tips, including horn-shaped and step-change flaring tips, which alter and improve the frequency response in BTE hearing aid instruments in which an ear canal tube without an attached ear mold is used. U.S. Pat. No. 6,275,596 issued to Fretz et al. is hereby incorporated by reference.
New arrangements and methods for pre-selecting the frequency response in the ear hearing instrument are constantly desired. The invention described below is an improvement in the physical characteristics of a hearing instrument by tailoring the sound passage from the receiver of the device to the user's eardrum to emphasize desired frequencies. A new geometric shape for the tip of an ear canal tube is disclosed which provides a dramatic improvement in the frequency response of BTE-type hearing instrument devices.
3. Identification of Objects of the Invention
A primary object of this invention is to provide a method and apparatus for tailoring the audio frequency response of a behind the ear (BTE) hearing aid instrument by altering the physical characteristics of the device to more accurately compensate for a user's specific hearing loss characteristics.
Another object of the invention is to provide an improved BTE hearing aid instrument in which a passage of cylindrical shape between the receiver of the device and the outlet of the device is replaced at least in part by a passage of non-cylindrical shape in order to alter the sound frequency of the instrument.
Another object of the invention is to provide an improved BTE hearing aid instrument in which a passage of cylindrical shape between the receiver of the device and the outlet of the device is replaced at least in part by a passage of one or more conical shapes to emphasize desired frequency ranges.
Another object of the invention is to provide a method of producing an improved BTE hearing aid instrument in which the passage between the receiver of the device and the outlet of the device is at least partially of a non-cylindrical shape and where the non-cylindrical shape is formed by rapid prototyping.
Other objects, features, and advantages of the invention will be apparent to one skilled in the art from the specification and drawings herein.